semax10,

True wheels and even tension don't necessarily mean the same thing. The LBS can vary tension across several spokes to true your wheel if your rim is not entirely round. This of course will result in uneven tension as you go around the wheel from spoke to spoke. Uneven tension is fine as long as the lowest tensioned the spoke is still sufficiently tensioned so that the spoke when in compression does not become slack enough to flex at the head. Continual flexing of the spoke will cause metal fatigue and breaking spokes which is what you are experiencing. That is why I asked if you have different tensions especially if your wheel had been trued up.